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As discussed in Section 1.3, sound diffusion is often employed to marginalise the acoustic influence of listening spaces and frequent lack of decoding transparency. Accordingly, acts of sound diffusion are often corrective, serving to present a soundfield similar to that which is heard during the compositional process. This point was raised by Jonty Harrison in a recent talk:

[...] sound diffusion (which grew up mostly around stereo works, but whose principles can be scaled up to embrace multichannel pieces) is primarily corrective – making as audible and available as possible to the listener what the performer knows to be there on the fixed medium and which is almost certainly compromised by the listening conditions of a public auditorium.

(Harrison 2011, p.5)

With this in mind, it seems reasonable to suggest that (at least some) acts of sound diffusion are corrective; we shall briefly consider the nature of such acts.

Throughout his various publications, Jonty Harrison identifies a range of sound diffusion techniques that may be employed to marginalise the effect of public listening spaces. Amongst these, he advocates the following approach for correcting the dynamic range; by raising and lowering the faders on the mixing desk, the human agent may, where necessary, correct what the composer intended:

[...] the composer will have indicated relatively louder and quieter events. [...] I would, at the very least, advocate enhancing these dynamic strata – making the loud material louder and the quiet material quieter – and thus stretching out

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the dynamic range to be something nearer what the ear expects in a concert situation.²⁸

(Harrison 1999b, pp.120-121)

Harrison goes on to discuss spatial images. He suggests that a (potentially large) number of loudspeakers may be activated to ensure that all members of the audience receive a spatial image that is more-or-less consistent with that intended by the composer and, with this in mind, he remains primarily focussed upon the corrective nature of diffusion. (Harrison 1999b, p.121). At this point, Harrison describes a particular loudspeaker configuration known as the main eight - as employed in a diffusion system known as BEAST (Birmingham ElectroAcoustic Sound Theatre) (Harrison 1999b) (see Appendix II). Harrison explains his rationale for the placement of these loudspeakers in relation to the corrective nature of sound diffusion; the various loudspeakers are positioned so that spatial images “can be perceived by everyone” (Harrison 1999a, p.3).

Most of Harrison’s various suggestions relate to stereo pieces. However, larger listening spaces, and the broader issues associated with the decoding of audio, also affect multichannel pieces, albeit differently; when presented in large, public listening situations, pieces of multichannel music are much more stable than their stereo counterparts. There are two main reasons for this. Firstly, multichannel pieces have a much larger dynamic range than stereo pieces; this invariably means that the acoustic influence of a larger space, which often reduces the dynamic range of the stereo pieces, has far less of an impact.

Secondly, multichannel pieces, which make use of an array of loudspeakers, may present the listener with extremely robust spatial images; the multichannel acousmatic composer may employ all of the various speakers within the array to create extremely detailed, multichannel spatial images and are often able to situate the listener within the array, thus avoiding issues related to the listener’s position relative to a stereo image. Accordingly, it is much easier for the

28 A similar point has been made by Denis Smalley: “In a recorded format you can never achieve an ideal dynamic range that will suit all spaces and contexts; maybe it is not even ideal on two loudspeakers. And so you need to exaggerate or highlight the high end – lift the top levels up – and possibly drop the low levels down. Extending the dynamic range affects peoples’

perceptions of the piece and permits and enhancing of the structural shape.” (Smalley 2000, cited in Austin 2000).

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performer to correct what they know to be there on the fixed medium, since the presentation is much less prone to spatial distortion. Corrective agential acts may be employed in the case of multichannel works. However, this typically involves relatively minor adjustments to the signal being sent to individual loudspeakers to ensure that the level is consistent across the multichannel array.

In some cases, the dynamic range may be enhanced across the entire array.

However, this is only really necessary in cases where the acoustic influence of the listening space is particularly extreme.

Linda Ferguson (1983), Stephen Davies (2004), Stan Godlovitch (1998) and Andrew Kania (2005) do not discuss sound diffusion and there is no evidence to suggest that they are aware of this practice. However, they would probably suggest that diffusion is in the service of the playback objective (as discussed in Section 1.3) and therefore largely consistent with their ontological theories. In some respects, this would be correct; sound diffusion is primarily corrective and often does seek to present the listener with a soundfield similar to that which was heard by the composer during the compositional process. With this in mind, one may suggest that sound diffusion is (at least on some occasions) in the service of the playback objective.

The above point requires some further consideration; sound diffusion may be primarily corrective. However, it is not merely corrective; rather than simply counteracting what is compromised by the listening conditions of a public auditorium, the human agent may take what is known to be there on the fixed medium as a point of departure. In other words, the human agent may seek to further dramatise, enhance, enlarge, exaggerate, expand and/or spatialise²⁹ what is one the fixed medium. In such cases, the agent moves away from the merely corrective towards the expressive³⁰ and thus severs any remaining links with the playback objective. The following section considers expressive agential acts and clarifies the distinction between the corrective and the expressive.

29 This set of examples is not comprehensive. It serves to highlight a distinction between corrective and expressive acts; a detailed discussion of the latter is to follow (Section 4.1).

30 The term expressive has been chosen (at least in part) because it is relatively ambiguous; we are not (yet) in a position to say what these agential acts are expressions of - are they expressions of the composer’s intentions? Or the music that is being performed? Or the human agent’s personal interpretation? These questions are answered in Chapter 3 and Chapter 4. For the time being, the term expressive, merely serves to highlight a distinction that holds between agential acts.

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